US20090314076A1 - Hybrid method for estimating the ground effect on an aircraft - Google Patents
Hybrid method for estimating the ground effect on an aircraft Download PDFInfo
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- US20090314076A1 US20090314076A1 US12/485,140 US48514009A US2009314076A1 US 20090314076 A1 US20090314076 A1 US 20090314076A1 US 48514009 A US48514009 A US 48514009A US 2009314076 A1 US2009314076 A1 US 2009314076A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M9/00—Aerodynamic testing; Arrangements in or on wind tunnels
- G01M9/02—Wind tunnels
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M9/00—Aerodynamic testing; Arrangements in or on wind tunnels
- G01M9/06—Measuring arrangements specially adapted for aerodynamic testing
Definitions
- the present invention relates to a method for assessing the aerodynamic ground effect on an aircraft.
- it is already known to determine the variation of at least one aerodynamic coefficient, such as the buoyancy coefficient, the drag coefficient, the pitching moment coefficient, etc., as a function of the height of the aircraft, in a range of height values between a value that is sufficiently high for the ground effect to be zero or negligible (value generally referred to as “infinite height” by aerodynamics engineers) and a zero value for which the aerodynamic ground effect is generally maximum, since the aircraft is taxiing on the ground.
- at least one aerodynamic coefficient such as the buoyancy coefficient, the drag coefficient, the pitching moment coefficient, etc.
- Such an experimental assessment has the drawback that the correction level provided by said correction coefficients is generally high in relation to the measured values of said aerodynamic coefficient, mainly at the center of said stream, such that the corresponding measurements are relatively inaccurate and unreliable. Furthermore, for model safety reasons, said model is not made to approach said floor by less than a minimum safety height, so that said model cannot be damaged or destroyed by collision with the floor under the effect of the vibrations generated by the airstream. There is therefore a need to extrapolate the variation of said aerodynamic coefficient between this minimum safety height and the floor (the ground). Such an experimental assessment cannot therefore give direct measurements of the ground effect, at the point where the latter is precisely at its most intense.
- the object of the present invention is to remedy these drawbacks.
- the method for assessing the aerodynamic ground effect on an aircraft by determining the variation of at least one aerodynamic coefficient of said aircraft as a function of the height, for a range of heights extending from an aerodynamically infinite height to a zero height is noteworthy in that:
- said set of heights for which the variation of the aerodynamic coefficient is determined by digital simulation corresponds to the low heights close to the ground and/or to the high heights close to said aerodynamically infinite height.
- FIG. 1 diagrammatically illustrates an airplane above the ground.
- FIG. 2 diagrammatically shows a model of the airplane of FIG. 1 positioned in a wind tunnel airstream.
- FIG. 3 is a diagram illustrating the method according to the present invention.
- FIG. 1 diagrammatically shows, from the front, an airplane AC above the ground G.
- the height H of the airplane AC relative to the ground G can vary from an infinite value Hinf, at which the aerodynamic ground effect is zero or negligible, to the zero value (the airplane AC is taxiing on the ground G) for which the aerodynamic ground effect is generally maximum.
- said aerodynamic coefficient is designated by C and its variation by dC.
- a model ac of the airplane AC is established and positioned in a wind tunnel airstream 1 limited by a floor 2 simulating the ground G, by a ceiling 3 , for which the distance D to the floor 2 can be sufficiently great to enable the simulation hinf of the infinite height Hinf, and by two lateral walls 4 and 5 (see FIG. 2 ).
- the aerodynamic coefficient c of the model ac corresponding to the coefficient C of the airplane AC, is measured for different heights h of said model ac less than the height hinf simulating the height Hinf of the airplane AC.
- the aerodynamic field of the model ac is limited, so that it is normal to correct the measurements of the aerodynamic coefficient c of the model ac (so-called “wall correction”).
- the model ac and/or the floor 2 present a risk of vibration, so that the model ac cannot be brought close to said floor 2 by less than a minimum measurement height hmin.
- the model ac makes it possible to obtain experimentally the variation dc of the aerodynamic coefficient c of the model ac as a function of the height h.
- the intermediate part of the variation dC of the aerodynamic coefficient C is obtained for the airplane AC, between the height Hcv (corresponding to hcv) and the height Hmin (corresponding to hmin).
Abstract
Description
- This application claims the benefit of French Patent Application 08 03428, filed on Jun. 19, 2008, which is hereby incorporated by reference.
- The present invention relates to a method for assessing the aerodynamic ground effect on an aircraft. For such an assessment, it is already known to determine the variation of at least one aerodynamic coefficient, such as the buoyancy coefficient, the drag coefficient, the pitching moment coefficient, etc., as a function of the height of the aircraft, in a range of height values between a value that is sufficiently high for the ground effect to be zero or negligible (value generally referred to as “infinite height” by aerodynamics engineers) and a zero value for which the aerodynamic ground effect is generally maximum, since the aircraft is taxiing on the ground.
- To do this, it is normal to perform an experimental assessment of said aerodynamic coefficient by producing a model of said aircraft and by placing said model in a wind tunnel airstream limited by a floor simulating the ground, by a ceiling and by two lateral walls. Said aerodynamic coefficient is then measured for different heights of said model in the airstream and measurements are corrected using correction coefficients to take account of the fact that the aerodynamic field of the model is limited by said floor, said ceiling and said lateral walls. Then, the variation of said aerodynamic coefficient of the aircraft is assessed as a function of the height based on said corrected measurements, performed on the model.
- Such an experimental assessment has the drawback that the correction level provided by said correction coefficients is generally high in relation to the measured values of said aerodynamic coefficient, mainly at the center of said stream, such that the corresponding measurements are relatively inaccurate and unreliable. Furthermore, for model safety reasons, said model is not made to approach said floor by less than a minimum safety height, so that said model cannot be damaged or destroyed by collision with the floor under the effect of the vibrations generated by the airstream. There is therefore a need to extrapolate the variation of said aerodynamic coefficient between this minimum safety height and the floor (the ground). Such an experimental assessment cannot therefore give direct measurements of the ground effect, at the point where the latter is precisely at its most intense.
- Moreover, attempts have already been made to assess the aerodynamic ground effect on an aircraft by a digital simulation aiming to reproduce by computation the physical reality of the flow of air around said aircraft. However, such a digital assessment has not currently proved reliable enough and accurate enough to be able to do away with wind tunnel tests in the intermediate part of the range of heights at which the measurements are carried out.
- The object of the present invention is to remedy these drawbacks.
- To this end, according to the invention, the method for assessing the aerodynamic ground effect on an aircraft by determining the variation of at least one aerodynamic coefficient of said aircraft as a function of the height, for a range of heights extending from an aerodynamically infinite height to a zero height, is noteworthy in that:
-
- said range of heights is subdivided into at least two consecutive sets of heights;
- for one of said sets of heights, the variation of said aerodynamic coefficient is determined by wind tunnel tests using a model of the aircraft; and
- for the other of said sets of heights, the variation of said aerodynamic coefficient is determined by digital simulation reproducing by computation the physical reality of the air flow around said aircraft.
- Thus, thanks to the present invention, it is possible, for each set of heights, to determine the variation of said aerodynamic coefficient as a function of the height with whichever of the two methods (experimental tests and computations) is the most accurate and the most reliable.
- Preferably, said set of heights for which the variation of the aerodynamic coefficient is determined by digital simulation corresponds to the low heights close to the ground and/or to the high heights close to said aerodynamically infinite height.
- In an advantageous exemplary implementation of the method according to the present invention:
-
- said range of heights is subdivided into three consecutive sets of heights;
- for that of these three consecutive sets which is in an intermediate position relative to the other two, the variation of said aerodynamic coefficient is determined by wind tunnel tests using said model; and
- for each of the other two sets, which are in a lateral position on either side of said intermediate set, the variation of said aerodynamic coefficient is determined by digital simulation.
- More specifically, when the wind tunnel tests are carried out in an airstream limited by a floor simulating the ground, by a ceiling and by two lateral walls, said model being displaced heightwise in said airstream without, however, approaching said floor by less than a minimum safety height, advantageously:
-
- said intermediate set of heights in which the variation of said aerodynamic coefficient is determined by wind tunnel tests corresponds to a range of heights in said airstream extending from said minimum safety height to a height at least approximately equal to that of the center of said stream;
- a lateral set of heights in which the variation of said aerodynamic coefficient is determined by digital simulation corresponds to a range of heights in said airstream extending from the zero height to said minimum safety height; and
- the other lateral set of heights in which the variation of said aerodynamic coefficient is determined by digital simulation corresponds to a range of heights in said airstream extending from said height at least approximately equal to that of the center of said stream to the infinite height at which the ground effect is zero or negligible.
- Thus, thanks to the hybrid method according to the present invention, the following benefits are obtained:
-
- a harmonious combination of computations and tests, by using the benefits of each of the methods: digital simulation provides the capacity to estimate the ground effect between infinity and the height of the center of the stream, on the one hand, and between the minimum height that can be reached in a wind tunnel and the ground, on the other hand; the wind tunnel tests, restricted between the height of the center of the stream and the minimum height that can be reached in a wind tunnel, provide the reliability and the accuracy of the experimental measurements;
- a reduction of the weight of the wall corrections in the ground effect compared to the conventional methodology, notably when approaching the center of the stream, which is more acceptable from a methodological point of view;
- replacement of the extrapolation to the full ground effect carried out in a purely mathematical manner in the conventional experimental methodology by digital simulation, which makes it possible to introduce physical principles into this contribution to the ground effect;
- the possibility of using all types of digital simulation, which makes it possible in particular to incorporate the advances that will be made in the future in this field as and when they occur; and easy incorporation in the current processes: the new methodology does not in fact require any change, neither in the wind tunnel process nor in the experimental data.
- The figures of the appended drawing will give a clear understanding of how the invention can be implemented. In these figures, identical references designate similar elements.
-
FIG. 1 diagrammatically illustrates an airplane above the ground. -
FIG. 2 diagrammatically shows a model of the airplane ofFIG. 1 positioned in a wind tunnel airstream. -
FIG. 3 is a diagram illustrating the method according to the present invention. -
FIG. 1 diagrammatically shows, from the front, an airplane AC above the ground G. The height H of the airplane AC relative to the ground G can vary from an infinite value Hinf, at which the aerodynamic ground effect is zero or negligible, to the zero value (the airplane AC is taxiing on the ground G) for which the aerodynamic ground effect is generally maximum. - To assess said aerodynamic ground effect, it is normal to determine the variation of at least one aerodynamic coefficient of said airplane AC, for example the buoyancy coefficient Cz, the drag coefficient Cx, the pitching moment coefficient Cm, and so on, between said infinite height Hinf and said zero value. Hereinbelow, in particular with regard to
FIG. 3 , said aerodynamic coefficient is designated by C and its variation by dC. - Also normally, to determine the variation dC of the aerodynamic coefficient C, a model ac of the airplane AC is established and positioned in a
wind tunnel airstream 1 limited by afloor 2 simulating the ground G, by aceiling 3, for which the distance D to thefloor 2 can be sufficiently great to enable the simulation hinf of the infinite height Hinf, and by twolateral walls 4 and 5 (seeFIG. 2 ). - The aerodynamic coefficient c of the model ac, corresponding to the coefficient C of the airplane AC, is measured for different heights h of said model ac less than the height hinf simulating the height Hinf of the airplane AC.
- Since the
wind tunnel stream 1 is limited by thefloor 2, theceiling 3 and thelateral walls airstream 1, the model ac and/or thefloor 2 present a risk of vibration, so that the model ac cannot be brought close to saidfloor 2 by less than a minimum measurement height hmin. - To remedy these drawbacks, in the example illustrated by the figures, only the measurements of the aerodynamic coefficient c performed between the center cv of the stream 1 (situated at a height hcv at least approximately equal to D/2) and the minimum height hmin are used.
- Thus, between the heights hcv and hmin, the model ac makes it possible to obtain experimentally the variation dc of the aerodynamic coefficient c of the model ac as a function of the height h.
- Based on this variation dc as a function of h, the intermediate part of the variation dC of the aerodynamic coefficient C is obtained for the airplane AC, between the height Hcv (corresponding to hcv) and the height Hmin (corresponding to hmin).
- In
FIG. 3 , where the curve F illustrating the variation dC as a function of the height H is represented, this intermediate part obtained by the measurements in thewind tunnel stream 1 is represented by the portion FM′ in chain-dotted lines, of the curve F. - On the other hand, the lateral parts FL1 and FL2 of the curve F, respectively corresponding to the ranges of heights O-Hmin and Hcv-Hinf, are obtained by digital computation as indicated hereinabove.
Claims (5)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0803428 | 2008-06-19 | ||
FR0803428A FR2932883B1 (en) | 2008-06-19 | 2008-06-19 | HYBRID METHOD FOR EVALUATING THE FLOOD EFFECT ON AN AIRCRAFT |
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US20090314076A1 true US20090314076A1 (en) | 2009-12-24 |
US7926340B2 US7926340B2 (en) | 2011-04-19 |
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US12/485,140 Active 2029-10-20 US7926340B2 (en) | 2008-06-19 | 2009-06-16 | Hybrid method for estimating the ground effect on an aircraft |
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FR (1) | FR2932883B1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102589840A (en) * | 2012-01-12 | 2012-07-18 | 清华大学 | Vertical or short-distance takeoff and landing aircraft ground effect test system |
CN103364170A (en) * | 2013-07-05 | 2013-10-23 | 北京航空航天大学 | Ground simulation predicting method and system for aeroelasticity stability |
CN103398835A (en) * | 2013-08-21 | 2013-11-20 | 中国人民解放军国防科学技术大学 | System and method for testing transient air film cooling heat flow on basis of hypersonic-velocity gun air tunnel |
US20140195210A1 (en) * | 2010-11-03 | 2014-07-10 | Benoit Calmels | Simulation method for determining aerodynamic coefficients of an aircraft |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2944623B1 (en) * | 2009-04-21 | 2011-06-10 | Airbus France | METHOD AND TOOL FOR SIMULATING THE AERODYNAMIC BEHAVIOR OF AN AIRCRAFT IN FLIGHT IN THE NEIGHBORHOOD |
KR101549526B1 (en) | 2014-03-12 | 2015-09-03 | 국방과학연구소 | Ground effect test apparatus built-in surface collision protection function |
US11181934B1 (en) | 2020-05-20 | 2021-11-23 | Honeywell International Inc. | Systems and methods for predicting ground effects along a flight plan |
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US5186415A (en) * | 1990-05-14 | 1993-02-16 | Qun Li | Aircraft having means for controlling the ground effect flying altitude by sensing air pressure on the surface of the wing |
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US6547181B1 (en) * | 2002-05-29 | 2003-04-15 | The Boeing Company | Ground effect wing having a variable sweep winglet |
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US20100280802A1 (en) * | 2009-04-24 | 2010-11-04 | Airbus Operations (S.A.S.) | Method of predicting the aerodynamic behavior of an aircraft element |
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RU2118269C1 (en) * | 1997-07-02 | 1998-08-27 | Вячеслав Васильевич Колганов | Aerodynamic profile of wing of wing-in-ground-effect machine |
FR2929724B1 (en) * | 2008-04-02 | 2010-04-30 | Airbus France | METHOD FOR DETERMINING THE FLOOD OUTPUT SPEED OF AN AIRCRAFT. |
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US3224265A (en) * | 1962-05-07 | 1965-12-21 | Aerojet General Co | Method for determining aerodynamic influence coefficients of a wing |
US3250121A (en) * | 1964-01-31 | 1966-05-10 | Conductron Corp | Helicopter ground proximity indicator |
US5089968A (en) * | 1990-01-26 | 1992-02-18 | The Boeing Company | Ground effects compensated real time aircraft body angle of attack estimation |
US5186415A (en) * | 1990-05-14 | 1993-02-16 | Qun Li | Aircraft having means for controlling the ground effect flying altitude by sensing air pressure on the surface of the wing |
US5457630A (en) * | 1992-11-18 | 1995-10-10 | Aers/Midwest, Inc. | System for onboard lift analysis and apparatus therefor |
US5781126A (en) * | 1996-07-29 | 1998-07-14 | Alliedsignal Inc. | Ground proximity warning system and methods for rotary wing aircraft |
US20040065246A1 (en) * | 2000-05-18 | 2004-04-08 | Allen Ken R | Wing in ground effect vehicle with endplates |
US6547181B1 (en) * | 2002-05-29 | 2003-04-15 | The Boeing Company | Ground effect wing having a variable sweep winglet |
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20140195210A1 (en) * | 2010-11-03 | 2014-07-10 | Benoit Calmels | Simulation method for determining aerodynamic coefficients of an aircraft |
US9317633B2 (en) * | 2010-11-03 | 2016-04-19 | Airbus Operations (Sas) | Simulation method for determining aerodynamic coefficients of an aircraft |
CN102589840A (en) * | 2012-01-12 | 2012-07-18 | 清华大学 | Vertical or short-distance takeoff and landing aircraft ground effect test system |
CN103364170A (en) * | 2013-07-05 | 2013-10-23 | 北京航空航天大学 | Ground simulation predicting method and system for aeroelasticity stability |
CN103398835A (en) * | 2013-08-21 | 2013-11-20 | 中国人民解放军国防科学技术大学 | System and method for testing transient air film cooling heat flow on basis of hypersonic-velocity gun air tunnel |
Also Published As
Publication number | Publication date |
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FR2932883A1 (en) | 2009-12-25 |
FR2932883B1 (en) | 2010-08-20 |
US7926340B2 (en) | 2011-04-19 |
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